1. Field of the Invention
The present invention relates to a plasma generating method for generating a plasma by inputting a high-frequency signal to a treating chamber through an impedance matching device, and also relates to a plasma apparatus and a semiconductor manufacturing apparatus for subjecting a predetermined treatment to an object by using the plasma generated.
2. Description of the Related Art
Generally, with regard to a plasma apparatus, even when a treating chamber itself has the common structure, the input impedance of the treating chamber changes according to the kind of an object in the treating chamber. Therefore, even if individual matching elements of a matching device body are moved to matching positions predetermined by the experiments or the experiences, there may occur a situation in which the impedance between a high-frequency generating unit and the treating chamber 5 cannot be accurately matched. In this state, a high-frequency signal S is not efficiently fed to the treating chamber, and the plasma may not be ignited. In case the plasma is not ignited, moreover, it becomes difficult to execute the treatment of the object promptly.
Also, when the impedance matching is conducted in the plasma apparatus according to the related art, the individual matching elements have to be moved to the matching positions by making the reflectivity come close to a reference value while repeating the feedback controls to control the positions of the individual matching elements individually. Therefore, the plasma apparatus according to the related art has a problem that it takes a long time to match the impedance. Moreover, the impedance matching actions have been ended at a time when the reflectivity reaches the reference value. This raises a problem that it is difficult to move the individual matching elements to the more complete matching positions although the individual matching elements have those complete positions.
The present invention has been conceived in view of that point to be improved and has a main object to provide a plasma generating method and a plasma apparatus, which can ignite a plasma efficiently and reliably. Another object of the invention is to provide a semiconductor manufacturing apparatus, which is enabled to execute a treatment promptly on an object by igniting the plasma efficiently and reliably.
The invention also has still another object to provide a phase difference detecting method and a measuring device, which can detect such a phase difference between a progressive wave and a reflected wave at a high speed as is necessary for determining the matching positions of individual matching elements in an impedance matching device. Further another object of the invention is to provide an impedance detecting method and a measuring device, which can detect such an input impedance of an impedance matching device at a high speed as is necessary for determining the matching positions in an impedance matching device connected with a directional coupler. Yet another object is to provide a coaxial type impedance matching device, which can increase the impedance matching speed of a matching object and make the impedance matching degree more complete.
To accomplish the above objects, according to a first aspect of the invention, a plasma generating method generates a plasma in a treating chamber by controlling a high-frequency generating unit to generate a high-frequency signal and by feeding the high-frequency signal to the treating chamber through an impedance matching device. The plasma generating method includes controlling the high-frequency generating unit to generate and feed a high-frequency signal having a lower power than that generating plasma, to the treating chamber;, measuring a reflectivity as a ratio of a reflected wave to a progressive wave between the high-frequency generating unit and the treating chamber in a state of feeding the high-frequency signal having the lower power than that generating plasma to the treating chamber, controlling the impedance matching device on the basis of at least the reflectivity measured to define a matching condition of the impedance matching device in which the reflectivity is not higher than a defined value, as a preset matching condition, controlling the impedance matching device, when the plasma is generated in the treating chamber, so as to satisfy the preset matching condition, and then controlling the high-frequency generating unit to generate and feed the high-frequency signal of the power generating the plasma, to the treating chamber.
Also, according to a second aspect of the invention, a plasma apparatus includes a high-frequency generating unit for generating a high-frequency signal, a treating chamber for generating a plasma therein when the high-frequency signal is fed thereto, the treating chamber for executing a predetermined treatment on a contained object with the plasma, an impedance matching device arranged between the high-frequency generating unit and the treating chamber, for matching an impedance therebetween, a measuring unit for measuring a reflectivity as a ratio of a reflected wave to a progressive wave between the high-frequency generating unit and the treating chamber, and a control unit for controlling the impedance matching device. The impedance matching device includes a cylindrical external conductor, a column-shaped internal conductor arranged in the external conductor so that an axis of the external conductor and that of the internal conductor are identical, dielectrics being movable in a longitudinal direction of the internal conductor and disposed in clearance between the inner face of the external conductor and the outer face of the internal conductor, and a moving mechanism for moving the dielectrics. The control unit controls the high-frequency generating unit to generate and feed the high-frequency signal having a lower power than that generating the plasma, to the treating chamber, controls the moving mechanism on the basis of at least the reflectivity measured in a state of feeding the high-frequency signal having the lower power than that generating plasma to the treating chamber, defines positions, at which the reflectivity is not higher than a defined value, of the dielectrics in the impedance matching device, as preset positions, and controls the moving mechanism, when the plasma is generated in the treating chamber, to move the dielectrics to the preset positions.
According to a third aspect of the invention, a phase difference detecting method includes inputting a first input signal and a second input signal, which are identical in frequency to each other and are different in phase from each other, generating a first generated signal and a second generated signal, which are identical in frequency to and different by a first reference phase difference from the first input signal, on the basis of the first input signal, generating a third generated signal and a fourth generated signal, which are identical in frequency and are different by a second reference phase difference from the second input signal, on the basis of the second input signal, mixing the first generated signal and the third generated signal to detect relative phase difference between the first generated signal and the third generated signal, as a first relative phase difference, mixing the second generated signal and the fourth generated signal to detect relative phase difference between the second generated signal and the fourth generated signal, as a second relative phase difference, and referring to a relationship prepared in advance among the first relative phase difference, the second relative phase difference, and a true phase difference between the first input signal and the second input signal, to detect the true difference.
In this case, it is preferable that the first reference phase difference is 90 degrees, and that the second reference phase difference is 0 degree.
According to a fourth aspect of the invention, an impedance detecting method including inputting a progressive wave and a reflected wave output by a directional coupler connected to an object to be connected, as a first input signal and a second input signal, which are identical in frequency to each other and are different in phase from each other, generating a first generated signal and a second generated signal, which are identical in frequency to and different by a first reference phase difference from the first input signal, on the basis of the first input signal, generating a third generated signal and a fourth generated signal, which are identical in frequency and are different by a second reference phase difference from the second input signal, on the basis of the second input signal, mixing the first generated signal and the third generated signal to detect relative phase difference between the first generated signal and the third generated signal, as a first relative phase difference, mixing the second generated signal and the fourth generated signal to detect relative phase difference between the second generated signal and the fourth generated signal, as a second relative phase difference; referring to a relationship prepared in advance among the first relative phase difference, the second relative phase difference, and a true phase difference between the first input signal and the second input signal, to detect the true difference, mixing the first generated signal and the third generated signal to detect an amplitude ration of the third generated signal to the first generated signal, mixing the second generated signal and the fourth generated signal to detect an amplitude ration of the fourth generated signal to the second generated signal, and detecting an input impedance of the object to be connected on the basis of the detected true phase difference between the progressive wave and the reflected wave, and the detected amplitude ratios.
According to a fifth aspect of the invention, a measuring device includes a first signal distributor for generating and distributing a first generated signal and a second generated signal, which are identical to each other in frequency and are different by a first reference phase difference from a first input signal inputted, on the basis of the first input signal, a second signal distributor to which a second input signal having the frequency identical to the first input signal and being different in phase from the first input signal is input, the second signal distributor for generating and distributing a third generated signal and a fourth generated signal, which are identical to each other in frequency and are different by a second reference phase, on the basis of the second input signal, a first mixing unit for mixing the first generated signal and the third generated signal to detect a relative phase difference between the first generated signal and the third generated signal as a first relative phase difference, a second mixing unit for mixing the second generated signal and the fourth generated signal to detect a relative phase difference between the second generated signal and the fourth generated signal as a second relative phase difference, and a detecting unit for detecting a true phase difference between the first input signal and the second input signal on the basis of the first relative phase difference and the second relative phase difference detected by the first mixing unit and the second mixing unit, the first reference phase difference, and the second phase difference.
In this case, it is preferable that the first reference phase difference is 90 degrees, and that the second reference phase difference is 0 degree.
Also, the measuring device may further include a directional coupler connected to an object to be connected, the first signal distributor, and the second signal distributor, and a calculation unit for calculating an input impedance of the object to be connected. The first input signal and the second input signal, which are output by the directional coupler, are input to the first signal distributor and the second signal distributor, respectively. One of the first mixing unit and the second mixing unit mixes the both generated signals to detect an amplitude ratio of the both generated signals. The calculation unit calculates the input impedance of the object to be connected on the basis of the true phase difference between the first input signal and the second input signal, which is detected by the detecting unit, and the detected amplitude ratio.
According to a sixth aspect of the invention, a coaxial type impedance matching device includes a tubular external conductor, an internal conductor disposed in the external conductor, a matching device body including a plurality of dielectrics being movable and disposed in clearance between an inner face of the external conductor and an outer face of the internal conductor, the matching device body disposed between a directional coupler and an object to be matched, a moving mechanism for moving the dielectrics, a storing unit for storing a data table in which an intrinsic impedance of the matching device body and a position of each of dielectrics are made to correspond, a measuring device, and a control unit for controlling the moving mechanism. The intrinsic impedance of the matching device body is controlled to a value corresponding to positions of the dielectrics in the external conductor. The measuring unit includes a first signal distributor for generating and distributing a first generated signal and a second generated signal, which are identical to each other in frequency and are different by a first reference phase difference from a first input signal inputted, on the basis of the first input signal, a second signal distributor to which a second input signal having the frequency identical to the first input signal and being different in phase from the first input signal is input, the second signal distributor for generating and distributing a third generated signal and a fourth generated signal, which are identical to each other in frequency and are different by a second reference phase, on the basis of the second input signal, a first mixing unit for mixing the first generated signal and the third generated signal to detect a relative phase difference between the first generated signal and the third generated signal as a first relative phase difference, a second mixing unit for mixing the second generated signal and the fourth generated signal to detect a relative phase difference between the second generated signal and the fourth generated signal as a second relative phase difference, a detecting unit for detecting a true phase difference between the first input signal and the second input signal on the basis of the first relative phase difference and the second relative phase difference detected by the first mixing unit and the second mixing unit, the first reference phase difference, and the second phase difference, the directional coupler connected to the matching device body, the first signal distributor, and the second signal distributor, and a calculation unit for calculating an input impedance of the object to be connected. The first input signal and the second input signal, which are output by the directional coupler, are input to the first signal distributor and the second signal distributor, respectively. One of the first mixing unit and the second mixing unit mixes the both generated signals to detect an amplitude ratio of the both generated signals. The calculation unit calculates the input impedance of the object to be connected on the basis of the true phase difference between the first input signal and the second input signal, which is detected by the detecting unit, and the detected amplitude ratio. The control unit calculates the input impedance of the object to be matched on the basis of the intrinsic impedance of the matching device body, which is obtained from the positions of the dielectrics in the matching device body and the data table, at a time of starting a matching operation, and the input impedance of the matching device body being as the object to be matched, which is calculated by the calculating unit of the measuring device, at the time of starting the matching operation, refers to the data table to calculate as target positions the positions of the dielectrics so that a conjugate impedance to the calculated input impedance of the matching device body and the intrinsic impedance are identical, and controls the moving mechanism to locate the dielectrics at the target positions, respectively.